Solid ink or phase change ink printers conventionally receive ink in a solid form, either as pellets or as ink sticks. The solid ink pellets or ink sticks are placed in a feed chute and a feed mechanism delivers the solid ink to a heater plate. The heater plate melts the solid ink impinging on the plate into a liquid that is delivered to a print head for jetting onto a recording medium or intermediate transfer surface.
In typical prior art feed channels, the sticks are positioned end to end in straight or linear channels or chutes with a melt device at one end and a spring biased push block on the other end. The space in solid ink printers, however, may be limited, and finding a location within the printer to accommodate a long straight chute for holding an ample supply of ink may be a challenge. The amount of ink that can be accommodated is limited by the physical dimensions of the printer and can not be greater with a linear ink loader than the length or width of available positions in the printer.
One method that has been used to increase the amount of ink that may be placed in a feed channel is to provide non-linear feed channels. The non-linear feed channels may include any number of linear and curved sections that can feed and guide ink sticks from an insertion end to a melt end of the feed channel. The non-linear feed channels typically include a feed mechanism, such as a belt, configured to move the ink sticks along the non-vertically oriented feed path of the channel. The use of rectangular sticks in channels that are curved or have an arcuate portion may result in buckling and camming of adjacent ink sticks in the feed channel.
Moreover, in previously known phase change ink jet printing systems, the interface between a control system for a phase change ink jet printer and a solid ink stick provided little information about the solid ink sticks loaded in the printer. For instance, control systems are not able to determine if the correct color of ink stick is loaded in a particular feed channel or if the ink that is loaded is compatible with that particular printer. Provisions have been made to ensure that an ink stick is correctly loaded into the intended feed channel and to ensure that the ink stick is compatible with that printer. These provisions, however, are generally directed toward physically excluding wrong colored or incompatible ink sticks from being inserted into the feed channels of the printer. For example, the correct loading of ink sticks has been accomplished by incorporating keying, alignment and orientation features into the exterior surface of an ink stick. These features are protuberances or indentations that are located in different positions on an ink stick. Corresponding keys or guide elements on the perimeters of the openings through which the ink sticks are inserted or fed exclude ink sticks which do not have the appropriate perimeter key elements while ensuring that the ink stick is properly aligned and oriented in the feed channel.
While this method is effective in ensuring correct loading of ink sticks in most situations, there are situations when an ink stick may be incorrectly loaded into a feed channel of a printer, newer ink loaders using larger sticks are particularly vulnerable to inappropriate use of earlier, smaller sticks. World markets with various pricing and color table preferences have created a situation where multiple ink types may exist in the market simultaneously with nearly identical size/shape ink and/or ink packaging. Thus, ink sticks may appear to be substantially the same but, in fact, may be intended for different phase change printing systems due to factors such as, for example, market pricing or color table. In addition, due to the soft, waxy nature of an ink stick body, an ink stick may be “forced” through an opening into a feed channel. This is easily done with earlier, smaller size sticks, most of which have a different, non-compatible, ink formulation. The printer control system, having no information regarding the configuration of the ink stick, may then conduct normal printing operations with an incorrectly loaded ink stick. If the loaded ink stick is the wrong color for a particular feed channel or if the ink stick is incompatible with the phase change ink jet printer in which it is being used, considerable errors and malfunctions may occur.